256 
NATURE 
[ FEBRUARY 24, 1923 

newly exposed surface of the molten substratum 
again solidified, a fresh crust, of greater density 
than before, would be formed out of the heavy 
substratum over the middle of the area, where the 
hollow had been made, and also in the channels 
between the fragments which had floated towards 
it; the Atlantic being the chief of these channels.” 
In his paper on “‘ The Place of Origin of the Moon 
—The Volcanic Problem’ (Journ. Geol., 1907, 
vol. 15, p. 23) W. H. Pickering elaborates the view 
previously propounded by Osmond Fisher; and 
although he makes no acknowledgment, we may 
safely infer that, directly or indirectly, he owed 
the idea to Fisher. The following quotation shows 
how remarkably close Pickering got to the statement 
of the Wegener hypothesis: ‘A curious feature 
of the Atlantic Ocean is that the two sides have in 
places a strong similarity. . . When the moon 
separated from the earth, three-fourths of the crust 
was carried away, and it is suggested that the 
remainder was torn in two to form the eastern and 
western continents. These floated on the liquid 
surface like two large ice-floes.”’ 
In his paper on the “ Bearing of the Tertiary 
Mountain Belt on the Origin of the Earth’s Plan” 
(Bull. Geol. Soc. America, 1910, vol. 21, p. 179) 
F. B. Taylor remarks: ‘‘ Thus we may conclude, 
at least provisionally, that it was North America 
that moved away from Greenland, and not vice 
versa.” 
If the view that the American continent has 
drifted away from Europe and Africa during Mesozoic 
and Tertiary times comes to be established, which 
seems highly improbable, it will no doubt owe much 
to Wegener, and will be associated with his name 
in this special sense ; but Osmond Fisher is clearly 
the author of the hypothesis of continental drift, 
so far as it applies to the problem of the origin of 
the Atlantic Ocean. The tectonic evidence provided 
by a study of the Atlantic floor, however, indicates 
that its submergence in large part during Tertiary 
times has been effected by the ordinary process of 
subsidence, and that, pari passu with this subsidence, 
considerable areas of Eurasia and Africa, which 
were previously submerged, have been raised above 
sea-level. Indeed, as Suess has pointed out, the 
evidence seems to show quite conclusively that, 
throughout the Mesozoic and Tertiary eras, a 
mediterranean ocean of the Atlantic type has in 
a large way dissected the continental masses and 
absorbed their drainage, although its orientation 
has changed. 
These broad geotectonic considerations seem to 
be utterly at variance with the claim based by 
Wegener on the jig-saw relationship of the opposite 
sides of the Atlantic; and there can be little doubt 
that, to a large extent, they dispose also of the Fisher 
hypothesis of continental drift, so far as the origin 
of the Atlantic is concerned. 
It should be remembered, however, that Fisher’s 
views on continental drift were based on the hypothesis 
he entertained as to the condition of the earth’s 
interior. There are profound differences between the 
Atlantic and Pacific Oceans. Astronomers tell us 
that the Fisher hypothesis as regards the Pacific 
is a very good one, and to this may be added the 
claim that, in large measure, it fits the facts known 
to us concerning the petrology and tectonics of the 
earth. While, therefore, declining to accept Fisher’s 
hypothesis of continental drift to explain the origin 
of the Atlantic, we may accept provisionally his 
view that the Pacific owes its origin to the detachment 
of the moon, especially as some hypothesis seems 
to be necessary to explain the heterogeneity of the 
earth’s crust. T. Croox. 
NO. 2782, VOL. 111] 

Aster tripolium on Salt Marshes. 
I Notice in the article on Belgian botany in NATURE 
of January 20, p. 97, a statement which reminds 
me of some observations of mine at Dovercourt, 
near Harwich, in 1908. The article says that a 
fringe of the purple-rayed form of Aster tripolium 
occurs between the salt marshes, occupied by the 
yellow form, and the more fertile, less saline, soil. 
At Dovercourt there are fields overflowed by the 
sea at every high tide, but still showing signs of 
former cultivation. The specimens of Aster growing 
here were all fleshy and rayless. Separated from 
these fields by earthen dykes were other fields, 
which showed no signs of being flooded at any time. 
Here the Aster was always thin and wiry in the 
stalk, and bore a well-developed ray. ¢ 
H. W. CHAPMAN. 
Cawthorne, Jordans Village, 
Beaconsfield, Bucks, 
January 31. 

The Cause of Anticyclones. 
Wir reference to Miss Catherine O. Stevens’ letter 
(NATURE, February 3, p. 150) on this subject, it is 
clear that there could be no high-pressure areas 
unless there were low-pressure areas as well. 
It is also quite clear that the pressure distribution 
at any moment depends upon the flow of the winds, 
the inertia of the air, and the rotation of the earth. 
But the atmosphere is a viscous substance, and the 
friction resulting from its viscosity would soon 
bring the whole mass to rest were there no continuous 
source of power to keep it moving. 
It is generally agreed that the source of power 
which maintains the circulation of the atmosphere 
is difference of air density resulting from difference 
of temperature. The problems to be solved are— 
what is the exact distribution of temperature through- 
out the atmosphere? will the actual temperature 
distribution account for the winds ? and how are these 
temperature differences maintained ? ; 
R. M. DEELEY. 
Tintagel, Kew Gardens Road, Kew, Surrey, 
February 2. 

The High Temperature of the Upper Atmosphere. 
In a letter in Nature of February to Mr. Whipple 
suggests that a comparatively sudden increase in 
temperature of the air at a height of about 60 kilo- 
metres, such as observations of meteors render 
likely, would account for the well-known zones of 
audibility and silence. This seems to us a promising 
line of investigation, which might enable one to 
determine annual variations of temperature, if any. 
We had already examined the possibility of using 
meteor observations for this purpose, but they are 
as yet scarcely sufficiently accurate to enable one to 
determine the small differences involved. The same 
applies to the suggestion of Mr. Deeley in NATURE 
of January 20. 
In the last paragraph of his letter Mr. Whipple 
suggests that the estimates which we made of the tem- 
perature on theoretical grounds require modification, 
as the atmosphere is exposed to the sun only during 
the day-time. We need scarcely point out that this 
fact had not escaped our attention and was allowed 
for in the coefficients of the formula actually used. 
F. A. LINDEMANN. 
Gorpvon M. B. Dogson, 
Clarendon Laboratory, Oxford, 
February 12. 

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